I would say that comparing dungeons and creature mechanics is like apples and oranges though. And besides we don't have any idea how many people are working on dungeons this time around so it's not really relevant. For all we know there are 30 people in five man teams fleshing out the entirety of each major region. Since it's speculative it's moot.
So you agree that 1 person is not enough to develop dungeons? Then I guess you shouldn't be so happy with Bethesda as the developer of Oblivion, because that's what they chose. Which is the entirety of my point, that the division of labor a lot more fractured than you'd think. If Bethesda has a 100 man team, 9 of them is 9%, and as a usable figure, about a tenth of their work force. Even IF dragons are the main focus of their game, there are still innumerable other aspects of the game to design, such as armor, weapons, animation, dungeons, exteriors, AI, creatures, races, lore, alchemy, magic, ranged combat, stealth...I could go on. Obviously some of these can be taken care of by 1 or 2 guys. But many others need a solid team of at least 3+, but probably not more than 5. So if you have 9 guys working on dragons, you have potentially 4 groups that are missing a guy, or anywhere from 1-4 groups that don't exist. And instead you have 9 guys picking their noses, getting bored, making origami footballs because there's really only so much you can put into one feature, no matter how large it is.